Switching apparatus for a phased transducer array

ABSTRACT

Analog switching apparatus electrically focuses a phased transducer array by interconnecting the outputs of selected transducer elements with selected taps of a multitapped electrical delay line. A first portion of the switching apparatus selects a subset of the transducer array to define a focusing search sector, and a second switching apparatus portion sequentially advances through a complete switching cycle for each transducer subset selection to traverse the focus of the array across the search sector in discrete increments.

ilnited @tafies Patent Wohi et all. [45] July 11, 1972 [54] SWHTCHHNGAPPARATUS FUR A [56] References Cited PHASED TRANSDUCER AY UNlTED STATESPATENTS [72] Inventors: Charla J. Wohl, Englewood Cliffs, N.J.;3,526,872 9/1970 Gulick, Jr. et a]. ..340/6 Jonathan L. Schere,Hartsdale; Thomas V. Costello, Bronx, both of NY. PrimaryExaminer-Richard A. Farley [73] Assignee: Edco Corporation, CollegePoint, NY. Attorney -DavlS Home Falthfun & Hapgood [22] Filed: Nov. 10,1969 ABSTRACT [21] APPL 875,315 Analog switching apparatus electricallyfocuses a phased transducer array by interconnecting the outputs ofselected transducer elements with selected taps of a multitapped elec-[52] U.S.Cl. ..340/6 R, 340/ 16R, 343/ 1 l5 trical delay line. A firstportion of the switching apparatus [51] Int. Cl G01s 3/00 ects a bset ofe transducer array to define a focusing [58] Field of Search ..340/6 R,16 R; 343/ 16R, [00 SA, Search sector, and a Second Switching apparatusPortion 343/1 15 sequentially advances through a complete switchingcycle for each transducer subset selection to traverse the focus of thearray across the search sector in discrete increments.

5 Claims, 5 Drawing Figures Z5, 3 62 I0. INPUT Z I sw/rcm/w; 25 3/ s gir621 DELAY d f fa h/ M4 m/x 2 I f 2 MATRIX 1 LINE E /IE5 SW/ 2; 5 3/ g 59/[7I/}fl r/nh f "4 1 aurpur 6/ SWITCH aur ur com 1001. urn. IZA T/ONCIRCUIT MEANS SWITCHING APPARATUS FOR A PHASED TRANSDUCER ARRAY Theinvention relates to switched transducer assemblies and, morespecifically, to an improved switching arrangement for electronicallyphasing an array of transducers.

Two basic antenna, hydrophone, or other receiving transducerconfigurations have been employed for scanning about a transducerlocation to acquire signals from unspecified (or hostile) source orsources. The first, older method employs a directional receivingtransducer which is continuously rotated about its axis. The orientationof the transducer when a signal is received identifies the relativebearing from the transducer to the signal producing source. Suchsystems, however, are limited in accuracy by the angular width of thereceiving transducer response pattern; have limited scanning speedssince transducers, sometimes of relatively massive size, must bephysically rotated; and are subject to mechanical wear, breakdown, andmounting and drive problems by reason of their mechanical rotationalrequirement.

The second widely employed transducer arrangement employs an array ofbroad or omnidirectional receiving transducers which are physicallystationary. The outputs of the transducer elements are steered, or gatedby switching apparatus through appropriate delays whereupon they areadditively combined. The combined outputs of the delay elements providea measure of any plane signal wavefront which may have approached thetransducer array from a particular direction a short time previouslycorresponding to the longest time delay employed.

The specific azimuth instantaneously scanned by the transducer array isdetermined by a selection ofa particular subset of the transducers, andby the particular interconnection of the selected transducers with thesignal delaying elements which are characterized by varying time delays.The scanning direction may be quickly changed by varying the connectionpattern between the transducers and the delay elements. This variationmay include a cyclic series of interconnection to scan in a circle (or athree-dimensional transducer array) or any other desired pattern.Further, the array may be quickly focused in a specific, predetermineddirection by instituting appropriate connections.

One widely employed switching arrangement heretofore employed inscanning for underwater acoustical signal sources has employed amechanical rotating switch to cyclically interconnect a plurality ofhydrophone staves with the taps of a multitapped delay line. The outputof the delay line provides a measure of incoming acoustical planewavefronts along an instantaneous sensing axis electrically determinedby the transducer-delay line interconnections which, in turn, aredetermined by the spatial orientation of the rotating element.

The rotating switch includes a series of commutating brushcontactinterface switches for effecting all of the appropriate scanninginterconnections during each complete switch rotation. To examine anysingle axis, the switch is positioned, as by a servomechanismarrangement, to reside along the desired 8X15.

However, such mechanical switches are subject to mechanical breakdownand, at best, require periodic down (inoperative) time for contact andbrush cleaning by skilled personnel. Also, brush wear, dirty contactsand the like increase the switch contact impedance thereby generatingerrors in the analog signals being commutated. Further, errors areproduced in scanning along a preselected axis by switch positioninglimitations associated with feedback servo systems.

Accordingly, it is an object of the present invention to provide animproved switching apparatus for effecting the requisiteinterconnections in a phased transducer array.

More specifically, an object of the present invention is the provisionof a transducer switching arrangement which is highly reliable; whichmay be rapidly sequenced; and which employs relatively few switchingcross-points compared with prior art structures.

The above and other objects of the present arrangement are realized in aspecific, illustrative switching arrangement for sequentiallyinterconnecting selected receiving hydrophone staves with the taps on adelay line.,Assuming n staves and k delay line taps, the arrangementemploys only a small fraction of the n X k switching cross-pointsrequired for a nonblocking matrix to interconnect each hydrophone stavewith each delay line tap.

The switching arrangement employs a first set of matrices which connecta given subset of the staves to a set of output terminals. Thesematrices efiect a rough" azimuth selection process specifying thephasing, or focusing of the transducer array to a bounded angularsector. A second matrix is employed to distribute the set of selectedtransducer output terminals among the delay line taps. The second matrixis completely cycled to produce a number of interconnection patterns foreach setting of the first matrices, and essentially sweeps the arrayphasing across the sector range in discrete steps. Once completed, thefirst matrix structure is advanced one state to define a new focusingsector, and the second matrix is again completely cycled to sweep acrossthe second sector. The process is repeated, either intermittently orcontinuously, until the transducer array has been phased, or focusedthroughout its desired range of bearings.

The above and other features and advantages of the present invention arerealized in a specific, illustrative embodiment thereof, presented indetail hereinbelow in conjunction with the accompanying drawing, inwhich:

FIG. 1 depicts in block diagram form an illustrative phased transducerswitching arrangement embodying the principles of the present invention;

FIG. 2 illustrates in detail an input transducer selection matrix 20shown in the arrangement of FIG. 1;

FIG. 3 shows in detail an output switching matrix 30 shown in thearrangement of FIG. 1;

FIG. 4 illustrates a subgroup of cross-point switching elements for thematrices 20 and 30 of FIGS. 2 and 3; and

FIG. 5 depicts the control structure for the input matrix 20 and outputmatrix 30 of FIG. 1.

Referring now to FIG. 1, there is shown an illustrative phased receivingtransducer array 10 which receives signals from any selected direction(or from all directions via a scanning process), and which provides ameasure of a signal received along its focused axis at an outputterminal 61. For concreteness and without limitation, an underwaterenvironment will be assumed, with the transducers comprising a pluralityof n hydrophone staves 11 -11,, which are responsive to acousticalsignals. The apparatus of FIG. 1 is useful, for example, for underwatersurvey, exploration or military applications where the relative bearingfrom the array 10 to a sound source or sources is to be identified. Asound source as referred to herein may comprise one which directly emitsacoustical energy, or one which reflects energy emitted by a controlledsignal source.

The transducers 11 -11,, are preferably arranged in a circular patternto provide uniform signal acquisition for energy incident from anydirection, although any other physical hydrophone array may be employed.To search for signals assumed of plane wave form) approaching from anydirection only a subset of the hydrophones (e.g., one quarter or n/4)which proximately face the plane wavefront are employed. For example, tosearch for a signal 13 approaching the hydrophone array 10 within abounded angular sector 14 (of width 360/n degrees), the hydrophonesll,-11,,,,, may be employed.

The acoustical wave 13 within the sector 14 will impinge upon each ofthe hydrophones 11,11,,,,, at different times which depend upon theparticular direction of wave propogation. Accordingly, the hydrophonearray 10 may be focused to a particular direction within the sector 14,e.g., to that of the wave 13, by first selecting the hydrophones II -11by providing maximum delay for the output of hydrophone 11,; and byeffecting monotonically decreasing delays for the other hydrophonestaves 11 through ll to essentially converge the outputs from thehydrophone array Il -ll from a quarter circle to a detection axisbroadside to the incoming wave. Similarly, a 360/n degree angular sector16 adjacent to the sector 1 may be examined by a selection of n/4hydrophone staves 11 -1 1 and so on.

Selection of n/4 of the hydrophones 11 to examine a corresponding 360/ndegree sector is accomplished by an input switching matrix 20. Thematrix accepts the continuous analog output signals from the nhydrophones 11, and supplies the outputs from n/4 contiguous selectedhydrophones to n/4 output terminals 25,25,,, and via a plurality of n/4leads 31 -31, to an output switching matrix 30.

The output switching matrix 30 connects the outputs from the n/4selected hydrophones to a selected pattern of taps 62 of a delay line60. The delay line taps 62 provide differing delays in the time requiredfor a signal entering any tap to arrive at the delay line output 61.

As discussed above, the matrix 20 selects n/4 hydrophones 11 therebydefining a 360/n degree focusing sector for the phased hydrophone array.For any such sector selection, the output matrix 30 effects a pluralityof connections (scan mode) between the selected hydrophones and selecteddelay line taps 62 to incrementally vary the focus of the hydrophonearray across the sector. In general, as is well known to those skilledin the art, some of the taps 62 may not be connected for any particularstate of the matrix 30, while two or more other inputs may be bridged.Each sector may be subdivided as minutely as desired by providingsufficient states for the matrix 30 together with sufficient delayincrements.

The matrices 20 and 30 are sequenced by a switch control circuit 50which may be operated in either of two modes selected by a switch 122.In the simpler case, when a single, specific azimuth is to be examinedfor a possible signal source, a plurality of switches 55 may be manuallyset to effect the proper matrix 20 and 30 connections for electricallyfocusing the hydrophone array 10 along the desired azimuth. This focuswill be automatically instituted and maintained without the inherentinaccuracy associated with prior art servo systems. Also, the switches55 (which may comprise electronic switching devices) may be varied toredefine the focus of the array 10 to lie along a new bearing orbearings.

Correspondingly, when operated in a scan or search mode by an alternatesetting of the switch 122, the control circuit 50 establishesconnections in the input matrix 20 to select n/4 contiguous hydrophones11 thereby defining a search sector, and then cycles the matrix 30through a series of connection patterns to sweep the focus of thehydrophone array 10 across the selected sector. The circuit 50 thenupdates the matrix 20 constraining it to delete a hydrophone 11 at theend of the selected subset opposite to the direction of scanning, and toadd one hydrophone on the other end. This effectively redefines androtates the selected sector 360/n degrees in the scanning direction. Thecircuit 50 next recycles the switch 30 throughout its inventory ofstates to sweep the focus of the array 10 through the second sector. Thescanning process may continue indefinitely, or may be terminated after aportion of a circular sweep or after a predetermined number of completescans.

For any one setting of the matrices 20 and 30, the output terminal 61 ofthe delay line 60 will supply an output signal ifa signal source ispresent along the sensed azimuth. The strength of the analog delay lineoutput is proportional to the strength of the emitted signal, if any.The incidence of an output, together with information identifying thestate of the matrices 20 and 30 (e.g., the contents of a counter orregister in the control circuit 50 as discussed hereinbelow) when asignal is received identifies the relative bearing from the array 10 tothe source. These signals are supplied to a suitable output utilizationmeans, e.g., an alarm circuit, printer, cathode ray or other displayrecorder, data processing equipment, fire control system or the like.

An illustrative input switching matrix 20 is shown in FIG. 2 and mayillustratively includejp-by-n/j matrices 21 where the horizontal axesofthe matrices 21 are each connected to a different hydrophone 11 asshown. The composite matrix 20 further includes p n/4p-by-j matrices 23,where the horizontal axes of the matrices 23 are each connected to adifferent matrix 20 output terminal 25. Analog switches 28, shown indetail in FIG. 4 and considered in detail below, are disposed at allelectrical matrix intersections in the arrangement of FIG. 2.

To connect any desired subset of the hydrophones 11 to the matrix outputterminals 25, an appropriate group of n/4 crosspoint analog switches 28are closed, i.e., effect a cross-point connection. For example, to focusthe hydrophone array within the sector 14, the switches 28 and 29 areclosed to connect the hydrophone 11 to the terminal 25 via a lead 27 theswitches 28 and 29 closed to connect the hydrophone 11 to the terminal25 and so forth until the requisite n/4 hydrophone staves Il -11 areconnected to terminals 25,-25, respectively. Similarly, it is observedthat any other permissible connection pattern of n/4 contiguoushydrophones to the terminals 25 may be established by the blockingswitching structure of FIG. 2.

It is noted that a single n-by-n/4 matrix may be employed for the inputswitching matrix 20. However, the blocking, plural matrix switchingarrangement shown in FIG. 2 employs far fewer cross-points than such asingle, nonblocking matrix.

An analog cross-point switch 28, illustrative of all crosspoint switches28 and 29 in FIG. 2, and also those in the output matrix 30 as well, maycomprise a field effect transistor (FET) as depicted in FIG. 4. Thetransistor 80 includes source and drain terminals 81 and 82 connected tothe crosspoint defining matrix leads and a gate terminal 83 driven bythe control circuit 50. Depending upon the N or P nature of the FETchannel, and whether the device operates in an enhancement or depletionmode, one binary voltage level selectively supplied to the FET gate 83will render the sourcedrain channel a low impedance (switch closed) anda second level will cause the device 80 to exhibit a very high impedance(switch open).

Assuming that each 360/n degree sector is to be subdivided into yincrements, the delay line 60 may include (n/4)-y input terminals 62wherein y terminals 62 are dedicated to each of the n/4 input lines 31(and thus to each input switch 20 output terminal 25). Thus, the matrix30 sequentially connects each line 31 through its range of delays in ysteps to sweep through the sector specified by the input switch 20 in yincrements. An illustrative output switching matrix 30 for operation inthe above mode is shown in FIG. 3, and comprises n/4 horizontal axeseach linked by cross-points to a unique group of y dedicated delay lineterminals 62. Other delay line 60 tapping constructions, andcorresponding sequential connection patterns thereof to the hydrophones11, are well known to those skilled in the art. For such alternativearrangements, the matrix 30 simply comprises the requisite cross-pointarray to effect the successive connections between the terminals 25 and62.

The switching control circuit 50 is illustrated in FIG. 5 and includesan oscillator which supplies pulses to two cascaded counters (leastsignificant bits) and (most significant bits). The counter 105 has acount capacity y, and completely cycles through its y count states foreach of the n states of the counter 110.

Two series of NAND-gates 114 and 112-113 are controlled by a mode switch122 to reproduce at the outputs of NAND- gates 1l6117 either the counterstate (scan mode with the switch 122 grounding a lead to disable thegates 114) or the state ofy n switches 55 (fixed azimuth focus mode withlead 121 being grounded to disable the NAND-gates 112-113). Morespecifically, the output of the gates 116-117 sequentially advances atthe oscillator 100 rate to institute scan mode operation with the lead120 ground. Cor respondingly, the hydrophones 11 are focused along aparticular bearing dictated by the closure pattern of the switches 55when the lead 121 is grounded, the state of the switches 55 beingelectrically reproduced and maintained at the outputs of the gates116-117.

A command decoder 90 of any conventional configuration, e.g., aplurality of multiple input (log y input terminals) coincidence gateswith FET gate driver output stages, operates the matrix 30 cross-pointswitches in the manner described above to sweep the hydrophone focusthrough the sector determined by the operatively selected hydrophones11. In particular, the decoder for each FET cross-point gate may decodeand respond to those of the y counts at the output of NAND-gates 116,during which the associated FET is to conduct. Since many of thecross-points operate at the same times, these coincidentally operatedFET gates (note the dashed gauging indications in FIG. 3) may beoperated in parallel to reduce the decoding structure required.

Similarly, a corresponding matrix decoder-driver 95 decodes the outputof counter 110 (or the output of switches 55,, AQ55,, in the non-searchmode), and drives the FET cross-point switches 28 and 29 in the matrix20. As before, each FET gate may have its own decoder-driver structureto render the FET conductive during the appropriate count states; theFET gates operated during like count states may be connected in parallelto eliminate redundant decoding; and, since these FETs are operated forcontinuous bands of the n count states, they may be controlled by aflip-flop which is set during the first conducting state of a countsequence, and reset after the last state of the conduction countsequence. Since the decoder 90 is driven by the least significant bitsof the cascaded counters 105-110 and the decoder 95 is driven by themost significant bits, the matrix 30 completely steps the hydrophonefocus across each of the n sectors in y discrete steps. Thus, thescanning operation considered above is optionally effected by thecontrol circuit 50 of FIG. 5.

Thus, the arrangement of FIGS. 1-5 has been shown by the above to effectthe requisite connections for rapidly and efficiently varying orpredetermining the focus of a phased transducer array. The number ofswitching cross-points required for the arrangement of FIGS. l-5 is muchless than that dictated by the employment of a single nonblocking matrixto connect the hydrophones and the delay line taps. For example, wherehydrophones are selectively connected to a delay line having 65 taps,only 251 cross-points are required rather than the 48 X 65 3,120cross-points required by a unitary matrix, a savings of 92 percent.

It is to be understood that the above-described arrangement is onlyillustrative of the principles of the present invention. Numerousvariations and adaptations thereof will be readily apparent to thoseskilled in the art without departing from the spirit and scope of thepresent invention. For example, other analog switches, e.g., relaycontacts, may be employed as the matrix cross-point elements. Also, thetransducers 11 may comprise radio frequency or other nonacousticalresponsive elements operated in any environment. Also, a signal emittingtransducer may be employed, with the remote signal sources generatingreflections of the transmitted energy back to the receiver array 10. Inthis latter case, amplifiers with gated transmit-receive switchedconditions might advantageously be employed. Further, threedimensionaltransducer arrays may be utilized to focus the array inthree-dimensional space.

Moreover, the switching system may be driven in the reverse direction(an input signal applied at the output of the delay line) for targetsimulation, or for phased array directional transmission.

What is claimed is:

1. In combination in a phased hydrophone transducer arrangement, aplurality of hydrophones disposed in a circular array, each of saidhydrophones exhibiting a response characteristic which is substantiallyuniform for a broad range of bearings relative to said hydrophone, atapped delay line including an output terminal and a plurality ofinputterminals, a plurality of intermediate signal terminals fewer in numberthan said hydrophones, input analog signal switching means forconnecting a selected subset of said hydrophones to said intermediateterminals for defining an effective focusing sector for saidhydrophones, output analog switching means for connecting saidintermediate terminals to said delay line input terminals for defining aparticular sensing axis within said sector, control means forcontrolling said input and output switching means, said control meansincludes a source of repetitive pulses, a counter cycled by said pulsesource, and a command decoder including means responsive to the mostsignificant bits of said counter for controlling said input switchingmeans to operatively select differing subsets of said hydrophones andresponsive to the least significant bits of said counter for controllingsaid output switching means to effect a plurality of connection patternsbetween said selected hydrophones and said delay line input terminals.

2. In combination, an array of transducers each having a relativelybroad response characteristic, said array being capable of beingelectronically focused, delay means having an output terminal and aplurality of input terminals, said delay means including means foreffecting a characteristic delay between each of said input terminalsand said output terminal, input analog switching means for operativelyselecting a subset of said plural transducers thereby focusing saidtransducer array within an angular sector, output switching means forselectively connecting said selected transducers to said input terminalsof said delay means for defining a particular focusing direction withinsaid sector, control means for controlling said input and outputswitching means, said control means including a source of repetitivepulses, a counter cycled by said pulse source, and a command decoderincluding means responsive to the most significant bits of said counterfor controlling said input switching means to operatively selectdiffering subsets of said transducers and responsive to the leastsignificant bits of said counter for controlling said output switchingmeans to effect a plurality of connection patterns between said selectedtransducers and said delay means input terminals for each selection ofsaid transducers by said input analog switching means.

3. In combination, an array of transducers each having a relativelybroad response characteristic, said array being capable of beingelectronically focused, delay means having an output terminal and aplurality of input terminals, said delay means including means foreffecting a characteristic delay between each of said input terminalsand said output terminal, input analog switching means for operativelyselecting a subset of said plural transducers thereby focusing saidtransducer array within an angular sector, said input analog switchingmeans including matrix means having a plurality of cross-point analogswitches, which comprise field effect transistors, for convergingoutputs from said plural transducers at a fewer number of matrix outputterminals, output switching means for selectively connecting saidselected transducers to said input terminals of said delay means fordefining a particular focusing direction within said sector.

4. In combination, an array of transducers each having a relativelybroad response characteristic, said array being capable of beingelectronically focused, delay means having an output terminal and aplurality of input terminals, said delay means including means foreffecting a characteristic delay between each of said input terminalsand said output terminal, input analog switching means for operativelyselecting a subset of said plural transducers thereby focusing saidtransducer array within an angular sector, said input analog switchingmeans including matrix means having a plurality of cross-point analogswitches for converging outputs from said plural transducers at a fewernumber of matrix output terminals, output switching means forselectively connecting said selected transducers to said input terminalsof said delay means for defining a particular focusing direction withinsaid section, control means for controlling said input and outputswitching means, said control means including a source of repetitivepulses, a counter cycled by said pulse source, and a command decoderincluding means responsive to the most significant bits of said counterfor controlling said input switching means to opera tively selectdiffering subsets of said transducers and resp0nsive to the leastsignificant bits of said counter for controlling said output switchingmeans to effect a plurality of connection patterns between said selectedtransducers and said delay means input terminals for each selection ofsaid transducers by said input analog switching means.

5. A combination as in claim 4 wherein said delay means comprises amultitapped delay line.

llunn i mg UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION PatentNo, Dated ll,

. Thomas V. Costello Inventor(s) Charles J. wohl, Jonathan L. Schere,and

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Page 1, the Assignee, indicated as "Edco Corporation", should be-EdoCorporation--;

Column 1 line 3, "The" should be--This-;

Column 3, line 11; "31. 31/ should be- 31 "11 Column 4, line 16, "25 -25should be-- 1 mm "7' Column 5, line 16, "55 A 5S should be- 55 --55Signed and sealed this 6th day of February 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT- GOTTSCHALK Attesting Officer Commissionerof Patents

1. In combination in a phased hydrophone transducer arrangement, aplurality of hydrophones disposed in a circular array, each of saidhydrophones exhibiting a response characteristic which is substantiallyuniform for a broad range of bearings relative to said hydrophone, atapped delay line including an output terminal and a plurality of inputterminals, a plurality of intermediate signal terminals fewer in numberthan said hydrophones, input analog signal switching means forconnecting a selected subset of said hydrophones to said intermediateterminals for defining an effective focusing sector for saidhydrophones, output analog switching means for connecting saidintermediate terminals to said delay line input terminals for defining aparticular sensing axis within said sector, control means forcontrolling said input and output switching means, said control meansincludes a source of repetitive pulses, a counter cycled by said pulsesource, and a command decoder including means responsive to the mostsignificant bits of said counter for controlling said input switchingmeans to operatively select differing subsets of said hydrophones andresponsive to the least significant bits of said counter for controllingsaid output switching means to effect a plurality of connection patternsbetween said selected hydrophones and said delay line input terminals.2. In combination, an array of transducers each having a relativelybroad response characteristic, said array being capable of beingelectronically focused, delay means having an output terminal and aplurality of input terminals, said delay means including means foreffecting a characteristic delay between each of said input terminalsand said output terminal, input analog switching means for operativelyselecting a subset of said plural transduCers thereby focusing saidtransducer array within an angular sector, output switching means forselectively connecting said selected transducers to said input terminalsof said delay means for defining a particular focusing direction withinsaid sector, control means for controlling said input and outputswitching means, said control means including a source of repetitivepulses, a counter cycled by said pulse source, and a command decoderincluding means responsive to the most significant bits of said counterfor controlling said input switching means to operatively selectdiffering subsets of said transducers and responsive to the leastsignificant bits of said counter for controlling said output switchingmeans to effect a plurality of connection patterns between said selectedtransducers and said delay means input terminals for each selection ofsaid transducers by said input analog switching means.
 3. Incombination, an array of transducers each having a relatively broadresponse characteristic, said array being capable of beingelectronically focused, delay means having an output terminal and aplurality of input terminals, said delay means including means foreffecting a characteristic delay between each of said input terminalsand said output terminal, input analog switching means for operativelyselecting a subset of said plural transducers thereby focusing saidtransducer array within an angular sector, said input analog switchingmeans including matrix means having a plurality of cross-point analogswitches, which comprise field effect transistors, for convergingoutputs from said plural transducers at a fewer number of matrix outputterminals, output switching means for selectively connecting saidselected transducers to said input terminals of said delay means fordefining a particular focusing direction within said sector.
 4. Incombination, an array of transducers each having a relatively broadresponse characteristic, said array being capable of beingelectronically focused, delay means having an output terminal and aplurality of input terminals, said delay means including means foreffecting a characteristic delay between each of said input terminalsand said output terminal, input analog switching means for operativelyselecting a subset of said plural transducers thereby focusing saidtransducer array within an angular sector, said input analog switchingmeans including matrix means having a plurality of cross-point analogswitches for converging outputs from said plural transducers at a fewernumber of matrix output terminals, output switching means forselectively connecting said selected transducers to said input terminalsof said delay means for defining a particular focusing direction withinsaid section, control means for controlling said input and outputswitching means, said control means including a source of repetitivepulses, a counter cycled by said pulse source, and a command decoderincluding means responsive to the most significant bits of said counterfor controlling said input switching means to operatively selectdiffering subsets of said transducers and responsive to the leastsignificant bits of said counter for controlling said output switchingmeans to effect a plurality of connection patterns between said selectedtransducers and said delay means input terminals for each selection ofsaid transducers by said input analog switching means.
 5. A combinationas in claim 4 wherein said delay means comprises a multitapped delayline.